A decade after work began in the southern French countryside on the biggest-ever fusion research project, called ITER, assembly formally began July 28 on the vast and intricate machines that will merge isotopes of hydrogen at temperatures around 150 million C to create net energy.

If all goes as planned, the plant will be at full power in 2035, generating 500 MW with 50 MW of input energy.

So far, the project is about 50% over budget and running 10 years behind schedule, yet “the hardest part lies ahead,” says Bernard Bigot, director general of ITER Organization, which is running the project’s construction.

Building the huge machines to minute tolerances will be “like assembling a three-dimensional puzzle on an intricate timeline,” he adds. The name ITER is an acronym for the project's original name, the International Thermonuclear Experimental Reactor.

Weighing over three times more than the Eiffel Tower, the 23,000-tonne “Tokamak” fusion reactor is being delivered in modules from all over the world to the site near Saint Paul-lez-Durance,  75 km north of Marseille. The program is backed by the European Union, the U.K., Switzerland, China, India, Russia, South Korea, and the U.S.

Arrays of powerful magnets will be used to keep the super-hot isotopes away from the donut-shaped reactor walls. ITER’s intricate machine will be 30 m tall, 30 m in diameter and housed in a heavily reinforced-concrete, seven-floor building.

Construction of the ITER buildings ended this March, and the first of many major components arrived a month later. “I’m pleased to say since 2015 we are on track,” says Bigot, who was drafted in to control the program’s errant budget and schedule five years ago.

Explaining the delay then, an ITER spokeswoman said "it’s an R&D project which has scientists at the end of it." Scientists had not appreciated "some of the engineering realities," added an ITER physicist. Coordinating the procurement of “first-of-a-kind” equipment through various national agencies also hurt.

In January, SNC-Lavalin's Atkins unit was awarded a five-year extension for its role as ITER architect-engineer.

To take over at ITER, Bigot says he insisted on being given powers of decision and on pooling the various international agencies into an integrated team, ending their siloed operations. He also declared as physically impossible the-then deadline of achieving first plasma by 2020.
 
Because governments are supporting the project in cash and in kind, Bigot cannot give a precise final cost. However, extrapolating from the European Union’s known cash contribution, he approximates the cost at $22.6 billion at 2015 prices, 53% above the previous estimate on the same basis.

While Bigot’s overall schedule appears to be holding, he expects some delay because of the pandemic. Stopping work was not an option as restarting would have been “a nightmare,” he says. With production shutdowns in Italy and other disruption, he expects the “few months’ delay” to be recoverable.

Because of its Chinese partners, ITER had some forewarning of the pandemic, with planned continuation of operations where possible, says Bigot. With donations of masks from China and South Korea, the organization was able to provide some protection for the workforce.

This new phase of fusion research brings a century-old dream of clean, virtually free energy a step closer.

Producing the myriad components that will form the ITER facility has been “a profound story of human endeavor,” said U.S. Energy Secretary Dan Brouillette, on line for the assembly launch ceremony. He added, "the best is yet to come.”